Which horizon is partially altered parent material?

• A. B Horizon
• B. C Horizon
• C. O Horizon
• D. A Horizon

Answer: (B)

Partially altered parent material is the C horizon. In soil profiles, the C horizon lies beneath the more developed topsoil and subsoil horizons and represents the weathered but still recognizable parent material from which the soil above has formed. It shows some chemical and physical weathering, but not enough to create the distinct features of the A, E, or B horizons. The A horizon is the surface soil rich in organic matter; the E horizon (when present) is the eluviated layer; the B horizon is where materials have accumulated (illuviation) from above and shows stronger pedogenic alteration. The O horizon is organic litter on the surface, and the R horizon is unweathered bedrock. So the term “partially altered parent material” points to the C horizon.